1. Field of the Invention
The invention relates to welding apparatus and methods, and particularly to a method and tool for friction stir welding for welding a tube and tubesheet to provide a sealed tube-tubesheet joint in, e.g., a heat exchanger tube assembly.
2. Description of the Related Art
Fluid leakage between the tube and tubesheet joints in heat transfer or heat exchanger equipment is undesirable and should be avoided at all costs. In tube and tubesheet joints, the mixing of two or more fluids, or leakage of hazardous fluids, can be extremely dangerous, and potentially catastrophic. Conventional welding techniques for seal or strength welding are based on fusion methods that may result in a number of defects, such as cracking and porosity formation. Such defects may result in a newly fabricated heat exchanger assembly being taken out of service in a very short period of time.
Thus, a method and tool for friction stir welding solving the aforementioned problems is desired.